Process for the treatment of chitinaceous materials and for the deacetylation of chitin

ABSTRACT

Disclosed is a process for the deacetylation of chitin and a process for the treatment of chitinaceous materials to obtain chitin which processes are conducted in a non-saponifiable, non-aqueous, water insoluble liquid having a flash point greater than about 100° C., preferably a non-aromatic hydrocarbon. The process for the deacetylation of chitin comprises suspending chitin in the hydrocarbon liquid, preferably from about 0.02 g/cc to about 0.2 g/cc, mixing therewith an alkali metal hydroxide solution, and heating the suspension at a temperature at least about 70° C. for a period of time sufficient to obtain the desired degree of deacetylation. The concentration of alkali metal hydroxide in the alkali metal hydroxide solution is at least 30% by weight, preferably at least 40% by weight, and most preferably at least 50% by weight, and the quantity of alkali metal hydroxide is sufficient to provide an alkali metal hydroxide to chitin weight ratio from about (0.35)(AMHMW)/40 to about (2.5)(AMHMW)/, 40 where AMHMW is the molecular weight of the alkali metal hydroxide.

The present invention relates to a process for obtaining chitin fromchitinaceous materials and/or for the deacetylation of chitin.

BACKGROUND OF TH INVENTION

Chitin, the second most abundant natural biopolymer (after cellulose),is a significant structural component in the shells of crustaceans(e.g., crabs, lobster and shrimp), in the exoskeletons of insects and inthe cell walls of many microbes and higher fungi. Chitin is apolysaccharide consisting predominantly of unbranched chains ofβ-(1,4)-2-acetamido-2-deoxy-D-glucose (also known asN-acetyl-D-glucosamine) residues. It may also be regarded as aderivative of cellulose, in which the C-2 hydroxyl groups have beenreplaced by acetamide residues, and it resembles cellulose in many ofits properties. Its occurrence in nature and its isolation are welldocumented.

Chitin is an amorphous solid which is practically insoluble in water,dilute acids, dilute and concentrated alkalies, alcohol and otherorganic solvents. It is soluble in concentrated HCl, H₂SO₄, 78-97%H₃PO₄, and anhydrous HCOOH.

In the U.S. and most other countries, chitin is a greatly underutilizedresource and even a significant waste problem for the shellfishindustries. The amount of chitin potentially available from seafoodwastes in the U.S. was estimated at between 5000 to 8000 tons per yearby Hattis and Murray (Industrial Prospects for Chitin From SeafoodWastes, MIT Seagrant Report No. 27, MIT, Cambridge, Mass., August 1976).

Chitin is obtained or isolated from chitinaceous materials such as theshells of crustaceans by removing the associated minerals, principallycalcium carbonate, and proteins from the chitinaceous material. Theminerals are typically removed by reacting the chitinaceous materialwith an acid, generally hydrochloric acid, which produces a watersoluble chloride by-product. The proteins are typically removed byreacting the chitinaceous material with a base, generally sodiumhydroxide.

It has been recognized that chitosan formed by deacetylating chitin hasinteresting and potentially useful properties. Although chitins mayoccur in nature in a slightly de-acetylated form, that which has beenpurposely de-acetylated is usually called chitosan.

Chitosan is not a single, definite chemical entity, but varies incomposition depending on conditions of manufacture. It may be equallydefined as chitin sufficiently deacetylated to form soluble amine salts.

Solutions of chitosan may be highly viscous, resembling those of naturalgums. The cationic properties of the polymer lead to formation ofcomplexes with anionic polyelectrolytes such as carboxymethyl cellulose,and the reactivity of the amino group permits formation of stable gelswith a variety of cross-linking agents. Many potential uses for chitosanhave been developed, including flocculating agents for water and wastetreatment, an additive for drilling fluids, a chelating agent forremoval of traces of heavy metals from aqueous solutions, coating toimprove dyeing characteristics of glass fibers, wet strength additivesfor paper, adhesives, photographic and printing applications,thickeners, formation of fibers and films, and many others. Other usesand processes are described in U.S. Pat. Nos. 3,862,122; 3,922,260;4,018,678; 4,195,175; 5,010,181; and 6,310,188. Commercial developmentof chitosan has, however, been hampered by the cost of manufacture.

Chitosan was first described by E. Gilson (Berichte 28 821 (1895); Bull(3) 11 1099 (1894)) as prepared by heating chitin with concentratedpotassium hydroxide at 180° C., or by fusion with solid potassiumhydroxide. Later investigators, notably Rigby (U.S. Pat. No. 2,040,879,May 1, 1936), used alkali hydroxide, usually sodium hydroxide inconcentrations from 30 to 60 percent by weight and temperatures from 80°to 160° C., to produce deacetylated chitin products ranging from 20percent to complete deacetylation. In general, reaction times necessaryto obtain soluble products, i.e., chitosan, were found to vary inverselywith alkali concentration and temperature, but no consistent correlationof these variables seems to have been developed. In all cases, the ratioof sodium hydroxide solution to chitin used in deacetylation has beenhigh, amounting to three or more parts of alkali hydroxide on a 100percent basis per part of chitin. Agitation of the chitin-alkali mixtureduring reaction has also been considered necessary to obtain uniformityof product, and exclusion of air has been found necessary to minimizedegradation.

The combination of high alkali concentration, high ratios of alkalisolution to chitin treated, high reaction temperature, and agitationduring reaction results in high cost for the conversion of chitin tochitosan. High temperature and high alkali concentration requirecorrosion resistant apparatus, generally all nickel or nickel lined,adding greatly to equipment costs. High ratios of alkali liquid tochitin increase equipment sizes for equal chitosan production and addedchemical costs.

U.S. Pat. No. 4,195,175 discloses the process for the deacetylation ofground chitin to yield a soluble chitosan product, that compriseskneading the ground chitin with substantially 2 to 7 parts ofsubstantially 35 to 50 percent sodium hydroxide solution, heating theresulting mixture to substantially 40° C. to 80° C., packing the mixturein containers to expel entrapped air, sealing the containers anddisplacing residual air with nitrogen, holding the mixture in aquiescent state at substantially 40° C. to 80° C. for from substantially160 to 40 hours, removing the alkali solution, and washing and dryingthe resulting chitosan product.

U.S. Pat. No. 4,619,995 discloses that chitosan can be prepared by (a)dispersing chitin in a liquid medium of the group consisting ofisopropyl alcohol, n-butanol, isobutanol, methyl ethyl ketone, toluene,and ethanol-toluene mixtures containing at least 72 mole percenttoluene, (b) slowly adding a strong aqueous sodium hydroxide solution tothe stirred slurry over a period of 10 to 30 minutes and in a proportionto provide substantially five to nine mols sodium hydroxide per moleN-acetyl glucosamine units in the chitin (about 0.98 to about 1.75 gsodium hydroxide per g chitin), (c) heating the stirred slurry to atemperature in the range of 75° C. to 100° C. and maintaining this rangefor a period of 2.5 to 3.5 hours, and (d) allowing the slurry to cool toambient room temperature and to steep the chitosan in the caustic mediumfor a brief period, typically 0.5 to 1.0 hours. The liquid medium ischosen such that the chitosan produced is swollen by the sodiumhydroxide.

U.S. Pat. No. 4,574,150 discloses a process for the manufacture of adry, free-flowing, water soluble carboxylic acid complex of chitosanwhich includes the step of combining one part of chitosan with from 0.5to about 30 parts by weight of a liquid selected from the groupsconsisting of alkanes containing about five to about nine carbon atoms,monoketones, monoesters, mono- and di-ethers, mononitriles,mononitroalkanes containing two to four carbon atoms, normally liquidmono-, poly-chloroalkanes, and alkenes containing one to two carbonatoms.

SUMMARY OF THE INVENTION

The invention provides processes for obtaining chitin from chitinaceous(chitin-containing) materials and/or for the deacetylation of chitinwherein the deacetylation is conducted in a non-aqueous,non-saponifiable, water insoluble liquid in which the chitin andde-acetylated chitin are not soluble, preferably an oleaginous liquid.It is a feature of this invention that the quantity of alkali metalhydroxide required to effect the deacetylation is less than the quantityknown to be used in commercial practice.

The process for obtaining chitin from chitinaceous materials comprisessuspending the ground chitinaceous material in a non-saponifiable,non-aqueous, water insoluble liquid having a flash point greater thanabout 100° C. (212° F.) (hereinafter sometimes referred to as “NSNAL”),adding an acid, preferably an acid which produces a water soluble saltby-product, most preferably hydrochloric acid, and reacting the acidwith the chitinaceous material at a temperature sufficient to effect thedemineralization of the chitinaceous material, adding an alkali metalhydroxide in an amount sufficient to neutralize the acid and produce analkaline mixture of the demineralized chitinaceous material, heating themixture-containing the NSNAL to a temperature and for a time periodsufficient to deproteinate the demineralized chitinaceous material, andremoving the chitin from the NSNAL and water soluble by-products.Alternatively, the chitin can be deacetylated in-situ by suitableadjustment of the concentration of alkali metal hydroxide, time andtemperature to obtain the deacetylated chitin as disclosed hereinafter.

The process for the deacetylation of chitin comprises suspending theground chitin in a NSNAL, adding an alkali metal hydroxide and water (oran alkali metal hydroxide solution), heating the mixture to atemperature and for a time period sufficient to deacetylate the chitinto the desired degree of deacetylation (hereinafter sometimes referredto as “DDA”), and optionally, removing the deacetylated chitin from theNSNAL, and washing the deacetylated chitin free of water solubleby-products and excess alkali metal hydroxide.

It is an object of this invention to provide a process for thedeacetylation of chitin wherein the degree of deacetylation is fromabout 15% to about 100%, preferably from about 15% to about 95%, mostpreferably from about 20% to about 90%.

It is another object of this invention to provide a process for thedeacetylation of chitin wherein the amount of alkali metal hydroxide isno more than about [(2.5)(AMHMW)÷40] parts by weight of alkali metalhydroxide per part of chitin where AMHWM is the alkali metal hydroxidemolecular weight.

Another object of the invention is to provide an economical process forthe deacetylation of chitin.

Still another object of the invention is to provide a process forobtaining chitin from chitinaceous materials.

Yet another object of the invention is to provide a process forobtaining chitin from chitinaceous materials and for deacetylating thechitin.

These and other objects of this invention will be apparent to oneskilled in the art upon reading this specification and the appendedclaims.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof will hereinafter bedescribed in detail and shown by way of example. It should beunderstood, however, that it is not intended to limit the invention tothe particular forms disclosed, but, on the contrary, the invention isto cover all modifications and alternatives falling within the spiritand scope of the invention as expressed in the appended claims.

The compositions can comprise, consist essentially of, or consist of thestated materials. The method can comprise, consist essentially of, orconsist of the stated steps with the stated materials.

PREFERRED EMBODIMENTS OF THE INVENTION

It is known to deacetylate chitin by reaction of the chitin with astrong alkali metal hydroxide solution to hydrolyze the N-acetyl groupto the free amine group and the by-product alkali metal acetates. Sincethe alkali metal hydroxide solution swells the chitin particles,generally this has been accomplished commercially by reacting the chitinwith the strong alkali metal hydroxide solution using excessivequantities of the alkali metal hydroxide solution in order to maintainthe mixture in a liquid, mixable state. Upon removal of the deacetylatedchitin from the liquid, re-use of the caustic solution generallyrequires that the caustic solution be treated with additional alkalimetal hydroxide to replenish the amount lost in the reaction andeventually to remove the alkali metal acetate unless the solution isdisposed of without additional treatment. In addition, since the chitinis maintained in a liquid, mixable state in an excess of the alkalimetal hydroxide solution, it absorbs a large quantity of the solutionand this absorbed solution is removed with the chitin when it isrecovered from the solution. The absorbed caustic solution is thenwashed from the chitin during purification of the decetylated chitinwhich results in a caustic solution which has an insufficientconcentration of the alkali metal hydroxide for re-use in thedeacetylation process. Thus these prior processes are very expensive toconduct.

We have now found that chitin can be deacetylated with a causticsolution while suspended in a non-saponifiable, non-aqueous, waterinsoluble liquid in which the chitin and the deacetylated chitin areinsoluble. The quantity of the alkali metal hydroxide solution(hereinafter sometimes referred to as “AMHS”) used is sufficient toallow the chitin to swell in the solution such that the deacetylationcan occur without having to add an excessive quantity of the AMHS tomaintain the mixture in a liquid, mixable state.

The deacetylation process of the invention comprises (1) mixing chitinand an alkali metal hydroxide solution with a non-aqueous,non-saponifiable, water insoluble liquid, (2) heating the mixture to atemperature of at least 70° C., preferably at least 80° C., and mostpreferably at least 85° C., for a period of time sufficient todeacetylate the chitin to the DDA desired, (3) and, optionally, removingthe deacetylated chitin/AMHS mixture from the free NSNAL, (4) washingthe mixture to remove the non-reacted alkali metal hydroxide, alkalimetal acetate, and any other water soluble by-products produced; and (5)drying the deacetylated chitin.

The concentration of alkali metal hydroxide in the AMHS is at least 30%by weight, preferably at least 40%, and most preferably at least 50% byweight. A 50% aqueous sodium hydroxide solution is commerciallyavailable from sodium hydroxide manufacturers. The concentration ofsodium hydroxide can be increased by adding additional sodium hydroxideto the 50% aqueous solution. The separate addition of the alkali metalhydroxide and water to the NSNAL will generate the AMHS in-situ.

The quantity of alkali metal hydroxide must be sufficient to produce theDDA desired for the reaction time and temperature utilized. The rate ofdeacetylation will increase as the temperature is increased. The DDAincreases as the quantity of alkali metal hydroxide increases and as thereaction time increases.

The quantity of alkali metal hydroxide used generally will be sufficientto provide an alkali metal hydroxide to chitin weight ratio from about[(0.35)(AMHMW)÷40] to about [(2.5)(AMHMW)÷40], preferably from about[(0.5)(AMHMW)÷40] to about [(2.5)(AMHMW)÷40]. The preferred alkali metalhydroxide for use in the process of the invention is sodium hydroxide.Other alkali metal hydroxides include potassium hydroxide and lithiumhydroxide. Other basic substances such as ammonium hydroxide, calciumhydroxide, and organic bases such as polyethylene amines, pyridine andthe like may be utilized as the alkalinity reagent.

The quantity of chitin used in the process of the invention ispreferably the maximum amount which can be mixed in the non-aqueous,non-saponifiable liquid after the addition of the AMHS and the chitin.The AMHS will be absorbed by the chitin resulting in a swelling of thechitin. The swollen chitin can become “pasty” and “sticky” if anexcessive quantity of the AMHS is utilized. Thus, as the alkali metalhydroxide to chitin weight ratio increases, the maximum concentration ofchitin in the non-aqueous, non-saponifiable liquid will decrease.Generally the chitin concentration will range from about 0.02 to about0.2 grams per cubic centimeter of the non-aqueous, non-saponifiableliquid, i.e., about 2% w/v to about 20% w/v, preferably from about 2%w/v to about 15% w/v.

The reaction time need only be sufficient to produce the desired DDA.Generally a reaction time from about 30 minutes to about 240 minuteswill produce a DDA from about 15% to about 95% when the reactiontemperature is at least 70° C. and the quantity of alkali metalhydroxide used is sufficient to provide an alkali metal hydroxide tochitin weight ratio in the range from about [(0.35)(AMHMW)÷40] to about[(2.5)(AMHMW)÷40].

The decetylated chitin/AMHS mixture can be removed from the NSNAL byknown solid/liquid separation processes, such as filtration,centrifugation, decantation, siphoning, and the like. Preferably thedeacetylated chitin/AMHS mixture is screened out of the NSNAL resultingin a deacetylated chitin/AMHS/NSNAL semi-solid mixture which is thenmixed with water to remove the remaining free NSNAL from thedeacetylated chitin/AMHS mixture. The NSNAL can be recovered bysiphoning off the water and added back to the NSNAL removed in thescreening step and re-cycled for re-use. The deacetylated chitin ispreferably washed free of the alkali metal hydroxide and solubleby-products of the deacetylation reaction, and thereafter preferablydried. The drying step can be eliminated if desired when thedeacetylated chitin is to be used in an aqueous medium. Many uses of thedeacetylated chitin do not require the complete removal of the NSNALfrom the chitin.

Although the process had been described in terms of deacetylatingchitin, the process can be applied to de-mineralized natural sources ofchitin such as de-mineralized crab, lobster, crayfish and shrimp shellsto both de-proteinate and deacetylate the shells in one step.

The non-saponifiable, non-aqueous, water insoluble liquid having a flashpoint greater than about 100° C. used in the invention may be any suchliquid that can be maintained in the liquid state at the temperature atwhich the deacetylation is conducted. The water solubility should beless than about 3% by weight. The deacetylation reaction temperatureshould be at least 70° C., preferably at least 80° C., and mostpreferably at least 85° C. The deacetylation can be undertaken atambient pressure or in suitable pressurized vessels. In the latter case,the temperature can be greater than the ambient pressure boiling pointof the aqueous phase. The higher the temperature, the greater is therate of the reaction which may enable the concentration of alkali metalhydroxide to be reduced for any desired DDA.

The NSNAL should be water insoluble and have: a low viscosity at thereaction temperature; no reactivity to 50% by weight sodium hydroxide atthe reaction temperature; good oxidation stability; low sorption to thedeacetylated chitin; and a flash point greater than about 100° C. (212°F.). The NSNAL should be biodegradable and be easily recoverable.

The preferred NSNAL is an oleaginous liquid, most preferably anon-aromatic hydrocarbon or a non-aromatic hydrocarbon derivative whichis liquid at the deacetylation reaction temperature, non-saponifiable,and has a flash point greater than about 100° C. (212° F.).Representative hydrocarbons are saturated (paraffinic) hydrocarbons suchas n-alkanes and iso-alanes, un-saturated (olefinic) hydrocarbons suchas alkenes containing one or more double bonds, and mixtures thereof.Generally the hydrocarbon will contain at least fourteen carbon atoms.

Preferably the NSNAL is a relatively low viscosity hydrocarbon refinedfrom petroleum oil, most preferably primarily paraffinic hydrocarbons.Representative hydrocarbons can be obtained from Conoco Phillips fromtheir Pure Performance Base Oils (70N, 80N, 110N, 225N, and 600N—all 99%minimum saturated hydrocarbons) and ConoPurem Process Oils (3P, 4P, 6P,and 12P—all 99% minimum saturated hydrocarbons), from EXPO ChemicalCompany, Inc. for their HT 100 Paraffinic Process Oil, from Vassa AcetesY Solvente-Venezeulas S. A. for their Vassa-LP oils (LP-70, LP-90,LP-100, and LP-120), and other petroleum refiners.

Other non-limiting NSNAL which can be used in the process of theinvention are: high molecular weight alcohols, especially containingmore than about 8 carbon atoms, and other aliphatic hydrocarbonderivatives having the requisite characteristics; polypropylene glycols,propylene glycol ethers, butylene glycol ethers, and the like; andsilicone oils.

As indicated hereinbefore, it is another feature of the invention toprovide a process for obtaining chitin from chitinaceous materialswherein the chitinaceous material is (1) suspended in a NSNAL, (2)reacted with an acid to remove the minerals associated with thechitinaceous material, preferably an acid which produces a water solublesalt by-product, most preferably hydrochloric acid, and (3) reacted withan alkali metal hydroxide to deproteinate the chitinaceous material,and, preferably, to simultaneously deacetylate the chitin.

The deacetylated chitin (also known as partially acetylated chitosan)can be derivatized with various reagents as is known in the art toproduce polymers having various characteristics and utility.

The derivatizing reactions can be carried out either without catalystsor, in the acid pH range, in the presence of acid catalysts (for exampleacetic acid or hydrochloric acid), or in the alkaline pH range, in thepresence of bases (for example alkali metal hydroxides or tertiaryamines). When, for example, alkylating reagents are employed,derivatives are preferentially formed on the nitrogen when the processis carried out in a neutral or acid medium, and derivatives arepreferentially formed on the oxygen when the process is carried out inan alkaline medium.

The reaction times and temperatures are specific for the product of theparticular reagent employed, and largely correspond to the informationof the prior art.

The deacetylated chitin derivatives are worked up in a customary manner,for example by filtration or purification, for example in the form of anextraction of the by-products and the reagents which have been used inthe reaction and not consumed, and/or the agent in which the reactionhad been carried out, or by drying.

The reaction can be carried out with one or more reagent(s), which areemployed in combination or, alternatively, in succession. Ifappropriate, an intermediate isolation can be carried out, for examplewith filtration, purification and drying. Which process steps are to beselected depends largely on the end products to be prepared and can bedetermined without difficulty.

Examples of reagents which can be reacted with the deacetylated chitinare, for example, alkylene oxides, such as ethylene oxide, propyleneoxide, butylene oxide, glycidol, 1,2-epoxydodecane, 1,2-epoxyhexadecane,glycidyltrimethyl-ammonium chloride, glycidyl ethers (for exampleglycidyl isopropyl ether), alkyl halides (for example methyl chloride,ethyl chloride or stearyl chloride), acid anhydrides (for example aceticanhydride and succinic anhydride), vinyl compounds (for example methylvinyl ketone, acrylonitrile), aldehydes (for example acetic aldehyde,nonane aldehyde, glyoxylic acid), reactive halogen compounds (forexample sodium chloroacetate, β-chloroethane sulfonate, chlorosulfonicacid or carboxylic acid chlorides), phosphorus pentoxide, cyanamides andcompounds which can be grafted by means of free radicals (for example bydiallyldimethylammonium chloride or acrylonitrile) in the presence of afree-radical initiator. If multifunctional reagents are employed, theresults are crosslinked chitosan derivatives. The reaction withaldehydes is advantageously carried out in the presence of a suitablereducing agent, such as, for example, sodium cyanoborohydride, so thatthe N-alkyl derivatives are obtained directly.

Such deacetylated chitin derivatives can be used for a very wide rangeof purposes. They include the following: sludge drainage, applicationsin drilling fluids, thickener (for example in concrete compositions),auxiliaries in the paper and textile industries, absorbents (for examplefor water or blood), additives to foodstuffs and feed, manufacture ofmembranes, films and fibers, coating agents, plastics components,separating agents (for example for separating metal ions from aqueoussolutions), flocculating agents, application in chromatography,molecular sieves, application in cosmetics (for example for shampoos,toothpaste, hair sprays, nail varnish etc.), application in fungicides(for example in agriculture), use in immunology, in biochemistry (forexample for the immobilization or separation of enzymes) and inmedicine, as well as in medical equipment.

The following examples are provided for illustrative purposes and arenot intended to limit the scope of the invention.

The deacetylation of chitin in Examples 1-19 was conducted using thefollowing process steps:

(1) 300 ml of the oil indicated in Table A was heated to 93.3° C. (200°F.);

(2) 40 grams of crab shell chitin (DDA=6.5%) was added to the oil andthe stirring continued.

(3) The amount of sodium hydroxide (beads), water, and/or 50% by weightsodium hydroxide solution (S.G.=1.53) indicated in Table A was added andthe stirrer speed was increased as the chitin began to swell;

(4) The mixture was heated at 93.3° C. (200° F.) unless otherwiseindicated for the time indicated in Table A.

(5) The contents of the beaker were then drained over a 200 mesh screenand the volume of oil recovered was measured (indicated as RO #1) inTable A.

(6) The oil wet deacetylated chitin/NaOH mixture was then placed in alarge volume of water and hand stirred to separate the remaining oilfrom the deacetylated chitin, the oil siphoned off, and the volume ofoil recovered was measured (indicated as RO #2 in Table A);

(7) The deacetylated chitin was then washed thoroughly to remove theexcess sodium hydroxide followed by drying at 82.2° C. (180° F.) for 24hours.

The degree of deacetylation of the chitin was determined as follows:

Determining Percent Deacetylation of Chitosan by Direct Titration

A. Materials and Equipment:

1. Hydrochloric solution: 0.06 N

2. Sodium Hydroxide solution: 0.1000N

3. Distilled water.

4. A calibrated pH meter Note: MUST BE CALIBRATED DAILY

5. 300 mL Beaker

6. 25 mL Buret (increments of 0.1 mL)

7. Glass Pipet (10 or 25 ml)

8. Magnetic Stir Plate

9. Magnetic Stir Bars

10. Balance weighing in grams (readable to at least 2 decimal places)

B. Procedure:

-   -   1. Using a glass pipet, transfer 25.0 mL of 0.06 N HCl into a        glass beaker.    -   2. Add 0.10 g of moisture corrected chitosan and stir on        magnetic stir plate for 2 hours. (NOTE: To determine moisture        correction, take (0.10 g)(% moisture)÷100, then add that result        to 0.10 g.)    -   3. After 2 hours, pipet 25.0 mL of distilled water into the        beaker and stir for an additional 10-15 minutes.    -   4. After 10-15 minutes, place the calibrated pH probe into the        beaker and record the initial pH of the solution.    -   5. Fill the 25.0 mL Buret with 0.1000 N Sodium Hydroxide (making        sure to remove any air bubbles from buret, which could affect        the results).    -   6. While continuing to stir the solution, carefully titrate with        the 0.1000 N NaOH solution to a pH of 3.75—record this as V1        (volume 1).        -   NOTE: Carefully titrate in small increments while recording            the volume used and the pH after each addition of NaOH            solution.    -   7. Continue titrating to a pH of 8.00—record this as V2 (volume        2).    -   8. Run each sample in duplicate or triplicate if necessary        (Triplicate run is required if the difference numerically        between results is greater than 5).        C. Calculations

A. Calculating V1 and V2

NOTE: If the pH of 3.75 or 8.00 falls in between 2 amounts of titrantused, use the following formula to calculate the exact amount that wouldhave been used to achieve either 3.75 or 8.00.${f\quad(x)} = {{f\quad( X_{0} )} + {\frac{\lbrack {{f\quad( X_{1} )} - {f\quad( X_{0} )}} \rbrack}{( {X_{1} - X_{0}} )}( {X - X_{0}} )}}$Where, f(X₀)=the amount of titrant used immediately prior to achievingpH of 3.75 or 8.00.

f(X₁)=the amount of titrant used immediately after achieving pH of 3.75or 8.00.

X=3.75 or 8.00, depending on which pH is being calculated.

X₀=the pH value prior to getting 3.75 or 8.00.

X₁=the next pH value that is higher than 3.75 or 8.00.

B. Calculating the % Deacetylation

The following formula is used to calculate the percent deacetylation:% DA=[(V2−V1)*16116*N NaOH)]/mg of chitosan

NOTE: N NaOH=0.1000

-   -   mg of chitosan=100        C. Calculations:        Moisture Corrected Chitosan=(% moisture)(Chitosan,        g)÷100+(Chitosan,

The non-saponifiable, non-aromatic hydrocarbon liquids evaluated in theexamples are as follows: OIL A=HT 100 Paraffinic Process Oil availablefrom Expo Chemical Company, Inc., 6807 Theall Road, Ste. A, Houston,Tex. 77066; OIL B=Pure Performance® Base Oil 80N available from ConocoPhillips, P.O. Box 2197, Houston, Tex. 77252; OIL C=Vassa LP90 availablefrom Vassa Asocietes Y Solventes Venezulanos S. A., Torre Pequiven,Piso-1, Av Francisco de Miranda, Chacao, Caracas, Venezuela; OILD=Conoco 110 available from Conoco Phillips, P.O. Box 2197, Houston,Tex. 77252.

Set forth in Table A are the process conditions and results obtained fornineteen examples of the invention. The data indicate that thecharacteristics of the NSNAL, the concentration of the AMHS, thequantity of the AMHS, and the reaction temperature all influence thecharacteristics of the deacetylated chitin obtained, and that the NSNALis easily recovered for re-use. TABLE A Ex- ml Hr ample 50% g ml At mlml Ave % Number Oil NaOH NaOH H₂0 Temp. RO#1 RO#2 DA 1 A 20 — — 2 — — 202 A 20 — — 4⁽¹⁾ 200 100 22 3 A 20 — — 2⁽¹⁾ 200  80 25 4 A — 20 20 2 180120 29 5 A — 20 20 2 150 150 32 6 A — 20  5 2 200 100 38 7 A — 20 10 2180 120 49 8 A 40 — — 2 200 100 55 9 A 40 — — 4⁽²⁾ 200 100 63 10 A 80 —— 2 — — 70 11 B 80 — 40 2 260 — 36 12 B 20 — — 2 225  75 40 13 B 20 — —4 225  75 55 14 B 80 — — 2 260  40 79 15 B 40 — — 2⁽³⁾ 230  70 79 16 B40 — — 3⁽³⁾ 180 120 80 17 B 80 — — 4 245  55 82 18 C 20 — — 2 — — 30 19C 20 — — 2 200  80 25 20 D 66 — — 2⁽⁴⁾ — — 63 21 D 90 — — 2⁽⁴⁾ — — 62 22D 66 — — 2⁽⁴⁾ — — 69⁽¹⁾85 ± 2.8° C. (185 ± 5° F.);⁽²⁾87.8 ± 2.8° C. (190 ± 5° F.);⁽³⁾98.9° C. (210° F.);⁽⁴⁾82.2° C. (180° F.)

EXAMPLE 20-22

Shrimp shell chitin was deacetylated as in Examples 1-19 except thatthere were used 1000 cc of Conoco 110N oil; 22 grams of chitin inExamples 20 and 22 and 30 grams of chitin in Example 21; and 66 cc of50% sodium hydroxide in Examples 20 and 22 and 90 cc of 50% sodiumhydroxide in Example 21. In Example 20, the caustic solution was addedbefore the chitin. The reaction temperature was 82.2° C. (180° F.) andthe reaction time was 2 hours. The DDA of the deacetylated chitinobtained is set forth in Table A.

EXAMPLE 23

The process of obtaining chitin from a chitinaceous material and thedeacetylation of the chitin obtained is set forth in the followingexamples. The chitinaceous material utilized was ground shrimp shell.

1) Heat 300 ml of OIL A to 87.8° C. (190° F.);

2) Add 40 grams of shrimp shell and stir to keep the shell suspended;

3) Add 50 ml of 15% by weight HCl in 10 ml increments, allowing thegenerated foam to subside between additions;

4) Age overnight at ambient temperature;

5) Prepare a 50% caustic (NaOH) solution and heat to 93.3° C. (200° F.);

6) Heat the demineralized shell/oil mixture from step (4) to 93.3° C.(200° F.);

7) Add 40 ml of the heated 50% caustic solution while continuingstirring. Increase the mixer speed as necessary to maintain thedemineralized chitin/caustic solution in suspension;

8) Mix for 2 hours;

9) Drain over a 200 mesh screen and measure the volume of oil recovered−240 ml;

10) Pour the drained oil wet deacetylated chitin into a large volume ofwater and hand stir to separate the remaining oil from the deacetylatedchitin. Siphon off the oil layer and measure the volume of oil recovered−40 ml;

11) Wash the deacetylated chitin to remove the excess sodium hydroxideand water soluble by-products; and

12) Dry at 82.2° C. (180° F.) for 24 hours.

The DDA of the deacetylated chitin was determined to be 43%.

EXAMPLE 24

Shrimp shell chitin was deacetylated as in Examples 20-22 except thatthere were used 3500 cc of Oil D; 95 grams of chitin; and 285 cc of 50%by weight sodium hydroxide. The reaction temperature was 82.2° C. (180°F.). Samples of the deacetylated chitin were removed after 1, 1.5, 2,2.5 and 3 hours and the DDA determined for each. The percentdeacetylation was 49.8%, 54.5%, 56.9%, 56.8%, and 61.0%, respectively.

1. A process for the deacetylation of chitin comprising suspendingchitin in a non-saponifiable, non-aqueous, water insoluble liquid havinga flash point greater than about 100° C., adding thereto and mixingtherewith a saponification reactant selected from the group consistingof (1) an alkali metal hydroxide solution, (2) water and an alkali metalhydroxide to form an alkali metal hydroxide solution in-situ, and (3)mires thereof, and thereafter heating the suspension to a temperatureand for a time period sufficient to deacetylate the chitin to thedesired degree of deacetylation.
 2. The process of claim 1 wherein theconcentration of the alkali metal hydroxide in the alkali metalhydroxide solution is at least 30% by weight and wherein the quantity ofalkali metal hydroxide is sufficient to provide an alkali metalhydroxide to chitin weight ratio from about [(0.35)(AMHMW)÷40] to about[(2.5)(AMHMW)÷40] where (AMHMW) is the molecular weight of the alkalimetal hydroxide.
 3. The process of claim 2 wherein the concentration ofthe alkali metal hydroxide in the alkali metal hydroxide solution is atleast 40% by weight.
 4. The process of claim 2 wherein the concentrationof the alkali metal hydroxide in the alkali metal hydroxide solution isat least about 50% by weight.
 5. The process of claim 1, 2, 3, or 4wherein the quantity of chitosan is from about 0.02 to about 0.2 gramsper cubic centimeter of the non-saponifiable, non-aqueous, waterinsoluble liquid, wherein the temperature is at least about 70° C., andwherein the degree of deacetylation is from about 15% to about 100%. 6.The process of claim 1, 2, 3, or 4 wherein the quantity of chitosan isfrom about 0.02 to about 0.2 grams per cubic centimeter of thenon-saponifiable, non-aqueous, water insoluble liquid, wherein thetemperature is at least about 80° C., and wherein the degree ofdeacetylation is from about 15% to about 95%.
 7. The process of claim 1,2, 3, or 4 wherein the quantity of chitosan is from about 0.02 to about0.2 grams per cubic centimeter of the non-saponifiable, non-aqueous,water insoluble liquid, wherein the temperature is at least about 85°C., and wherein the degree of deacetylation is from about 20% to about90%.
 8. The process of claim 5 wherein the non-saponifiable,non-aqueous, water insoluble liquid is a non-aromatic hydrocarbon orderivative thereof which is liquid at the reaction temperature.
 9. Theprocess of claim 6 wherein the non-saponifiable, non-aqueous, waterinsoluble liquid is a non-aromatic hydrocarbon or derivative thereofwhich is liquid at the reaction temperature.
 10. The process of claim 7wherein the non-saponifiable, non-aqueous, water insoluble liquid is anon-aromatic hydrocarbon or derivative thereof which is liquid at thereaction temperature.